Petroleum oil refining



fliully described, we

Patented Dec. 20,1938

saunas rs'momuu on. ass-name sac n. nam Pittsburgh, and William sci-cu, Wilkinlbnrg, Pa, assignorl to Gulf Research UNITED STATES a Development company, corporation ol Delaware cation November 2', 1984,

No Drawing. Appli Pittsburgh, Pa, a

Sei'hINO. 751,259

1 Clalm- (CL 19$--13) is brought to a temperature at which stratification occurs,usuallybetween 100 F. and E, and the oil layer is separa from the solvent l0 layer thus romeo, t e oil layer :being ireed of residual solvent to" recover an improved refined oil; all as more iully hereinaiter set forth and as claimed. I i y In our copending application, serial No. 151,256 have disclosed advantageous processes for refiningpetroleum oils with ethylene dichloride. Thepresent invention is a modification of and improvement upon the methods there described, i By the, present methods, hereinafter more 7 obtain'substantial' and im- .portant improvements in the viscosity-index, viscosity-gravity constant, pour point, carbon residue and other properties of the oil. I

The viscosity-gravity relationship of oils is a as good criterion for judging an oiland is much used as a standard in determining the characteristics 0!, oils. See Hill and Ferris, Industrial an Engineering Chemistry, vol. 17, page 1250 925) and Hill and Coats, ibid. vol. 20, page 641 (June i928) Those authors explain the viscosity-gravity constant and its significance.

The viscosity index (Dean and Davis. on and Gas Journal, March 31, 1932, page 92) is also much used in characterizing the viscosity-tem- I perature relations oi'an oil, a high index indieating a fiat viscosity-temperature curve. The

- difierential solvents under discussion have a general efiect in lowering the viscosity-gravity constant and raising the viscosity index.

. 40 In addition to the improvement in tlie products obtained, the present processes have 'certain advantages over the refining of petroleum oils with ethylene dichloridealone. In themethods described in our above acknowledged applica- 45 tion Serial No. 751,256, the ethylene-dichloride is admixed with the 'oil' at ordinary temperatures I and then themixture is cooled to about 50 F. below the miscibility temperature toefiect stratification into an oil layer and a solvent layer. The

, 60 two layers are separated and" the ethylene dichloeach by distillation. By

ride is removed from distillingofl the ethylene dichloride, an improved refined c oil is obtainedandalso as a separate product, there is obtained a nsphthenic are completely With the introduction of good solvents, new dii- As there stated the miscibility temperature of ethylene dichloride with the ual oils varies between 28 and 15 1",; the exact temperature depending'uponthe particular oil and other factors.

In the present processes, in lieu of using ethylene dichloride alone, we usea'composite differ,- ential solvent composed of ethylene dichloride and anotherdifierential solvent of relatively high miscibility temperature characteristics, such as liquid sulfur dioxide, methyl cellosolve or iuriural. By using such a composite solvent, we obtain modified processes whichare advantageous. The presence of the second solvent in conjunction with the ethylene dichloride permits variations and adjustments in various steps of the process. is For instance, by controlling the proportions used. the miscibility temperature may be varied so that stratification can be obtained at higher temperatures, not necessitating refrigeration or a saving may be effected in the refrigeration required to cool the mixture. 4

The solvent extraction or petroleum oil, with various solvents,-h'asbeen heretofore proposedand practiced. One of the first solvents employed was liquid 80:. Liquid sulfur dioxide is a highly selective solvent but is oi limited utility because of its relatively low solvent power. Thus it will remove from an unrefined stock a small amount oi asphalt-like and highly naphthenic material leaving a high yieldjof a slightly imso proved product. This is not sufllcient for commercial purposes, as it is desired to produce a much improved product. .In order to effect this it is necessary to remove not only the small .proportion of asphaltic and naphthenic material, as larger volume of intermediate substances. Thissulfur dioxide is unable to eflect economically even by the use. of extensive amounts oisolvent and the resulting improvement of liquid oils is, for most heavy stocks, in- 40 suillcient.

To overcome that difilculty, it has been pro posed to add'to the SO: a good solvent for the oil' to obtain a mixture capable oi extracting more material. 'Good solvents, such as benzol, which miscible with the oil, are used.

flculties arise. Although a better removalof naphthenic bodies is obtained, the loss of good oil (paraflinieoil) is somewhat increased. so As stated incur copending application Serial No. 151,256, ethylene-dichloride isa differential solvent for the oil. Our new composite solvents contain two diflerential solventseach, whereas, their nearest analogue, the benz0l-SO; mixture ture.

benzene, furfural, phenol ,each give good results on comprises a good solvent and a differential solvent. Withv the new composite solvents, we minimize the loss of good oil with an increase in the solvent power. The addition of the selected dif ierential solvent raises the miscibility tempera- Thus, after adjusting the temperature to obtain stratification, the solvent layer comprises mixed liquids not miscible with the good oil.

By extracting oils with a composite solvent, containing ethylene dichloride and another .differential solvent of relatively high miscibility temperature characteristics, such as furfural or methyl cellosolve or- $02, we obtain amore com- 'plete extraction ofnaphthenic bodies, a better selectivity, a reduction in the loss of good oil and a higher yield of superior refined oil. All of these advantages cannot'be obtained in any one of the prior art processes.

Because of the wide diversity of lubricating oils stocks. to be improved, solvents of widely different characteristics are often necessary. This variation may be obtained by changing solvents, but such amethod is undesirable because usually each type of solvent requires a different plant 'installationior its use, and much additional investment would be required. Thus nitroand other solvents may certain stocks and not 7 on others; but it is not practical to shift quickly from-one solvent. to another. By. the use of mixtures of ethylene dichloride I with sulfur dioxide it is possible-to obtain wide variations in the characteristics of the composite solvent in hand without any change in plantirequirements or any additional investment. Thus where desired, light distillates'may be treated with sulfur dioxide alone; light naphthenicfilubricating distillates can be processed with mixtures comprising as little as 10 per cent ethylene dichloride and 90 per cent sulfur dioxide, while heavy paraiiinic stocks may require mixtures with sulfur mixture of ethylene dichloride with amount of the dioxide in the .orderv of 75 per cent of ethylene dichloride or higher for certain types of oils.

Extraction at low temperatures'is advantageous. and the above flexibility as to composition of solvents permits the use of rather wide temperature ranges. without impairing separation efliciency.

Similar advantages may be obtained by the furfurai or methyl cellosolve in appropriate proportions.

Inpracticing the present invention a suitable composite solvent is brought into contact with. the oil to be refined. This may be at a temperature above that at which the oil and solvent become completely miscible, with subsequent cooling, but in general it is at the temperature desired for the extraction. may be between say 100 F. and say 0 1". Thus. for most wax-bearing stocks. the extraction temperature is advantageously 75 F., while for dewaxed orQWax-free oils, it is conveniently 25 1".

the upper or ratio. and at the proper temperature or lower.v There is'a definite advantage in yield by workingat low temperatures. The mixed oil and solvent is held at this temperature longenough to permit clean stratification. the layers are separated and the extraction repeated on oil layer, as often as desired, say 3 or 4 times. Alternatively the extraction be a continuous one, the oil and solvent being pumped countercurr'ently in the proper volume through one or more mixing and settling 'chambe To recover the improved refined oil. the oil layer is freed 'of residual solvent,-u8ually by simple As the ratio is varied,

-be recovered in the process. Thirty-nine distillation. The distillation may be controlled to recover each of the solvents for re-use in the process. v e I Likewise, the solvent is recovered from the solvent layer for re-use in the process. After separating the solvent, there is obtained a useful nafihth'enic oil. i

In such processes, usuallybetween two and six volumes of composite solventfor one volume of oil are used. Composite diflerential solvents con- .t ng ethylene dichloride and SO: in ratios between 10:90 and ;25 are advantageous. For mostoil stocks, a ratio of 30:70 is satisfactory.

the miscibility temperature changes; the ,miscibility temperature is raised as the amount of S0: is increased. Analogous limits apply formixtures of ethylene dichloride with furfural and methyl cellosolve. For instance mixtures of ethylene dichloride with methyl cellosolve orfurfural in the proportions of 20:80 to :20 can be used successfully by making suitable adjustments of extraction temperatures. I

In a way, the ratios,.the volume of solvent and the stratification temperatures employed are somewhat dependent upon. whether dewaxing precedes or is subsequent to the solvent extraction.

From the above descriptionyit isbelieved persons skilled in the art .will understand the V311? ous applications and modifications of the generic invention. A further illustration of the generic invention is the following typical embodiment.

Example 1, parts of overhead cylinder stock from Qklahoma crude is mixed-at a temperature of 75", F, with 40 parts 60 parts of S02. maintained at that until clean stratification into an oil layer and a solvent layer is obtained. The lower solvent layer is withdrawn and the oil layer is extracted three more times with a like volume of said composite solvent.

'The separated oil of ethylene dichloride and The mixture is agitated and layer is then freed of solvent by distillation to obtain an improved refined oil. There areobtained 60.8- parts by weight of a refined oil having the properties, as compared with the original:

Original Refined oil 8 lilo gravity 0. 927 0.8044 ity at 210 seconds Seybolt 94 loom 3. tent 0 85 0 an m y cons Oerbonieeidne. percent 2.05 0.43

'Ihe ethylene dichloride and SO: removed from the good 011 by re-use in the process. Likewise, thesolvent may from the solvent layer for re-use and two-tenths parts of useful naphthenic oil is obtained when the solvent is so removed. The specific gravity of this naphthenic oil is 0.988- as compared with 0.927 on the original oil.

As stated ante in this specification, the oil may be previously or subsequently dewaxed in any appropriate manner as has been indicated.

in other ratios may be used. Likewise, the separation oi the oil-layer and .solvent layer may be effected at other temperatures so long as the temperature for half an hourv following distillation may be recovered. for- 9 In lieu of the composite solvent used in Example 1", mixtures of ethylene dichloride and SO:

temperature is sufiicient to produce a clean complete stratiflcaflon. Such by Example 2.

' Empie 2 it 5 100 parts of a naphthenic lubricating distillate from Gulf Coastal crude having a viscosity of '11 Saybolt at 210 F. is extracted at 50 F. with four successive portions of 100 parts each of a mixture comprising 30 percent ethylene dichlo' ride'and 70 per' cent liquid sulfurdioxide. This operation is performed under the vapor pressure of the mixture. The solventiis removed from, each layer by distillation and a refined oil product amounting to 65.3 parts of the charge is refrom the following properties of the original and refined oils.

Origins] oil I x 8 c 0.0M 0.000 meta 210 Saybolt 71 68 Viscosity indexms. 4 60 Viscosity gravity constant 0. 877' 0. 842 u Example 3 100 parts of overhead cylinder stock from Oklahoma crude are extracted with 200 parts'oi a mixture ethylene dichloride with methyl cellosolve in the ratio 70:30 at 32 FJ The ramnate layer so obtained is separated from the solvent layer and then twice extracted with 100 parts of the same solvent mixture in the same way. The

solvents were removed from the final rafllnate layer by distillation. The yield of refined oil was 52 parts by weight. The comparison of the original and the refined oil is as iollows;

points are illustrated moved. The improvement obtained is easily seen 0mm Reflncdoll 0.021 cam 180 98 mass cm trample 4 4 100 parts oi overhead cylinder stock from Oklahoma crude are extracted with 100 parts of a mixture of ethylene dichloride and furiural in the mm of 50:50 at We. Theraflinate layer- 5 is separated from the solvent layer and the extraction is repeated three times in the same man-' net". The solvents are removed from the final rafiinate by distillation. A yield of 63.9 parts by weight .01 refined oil is obtained. The comparison 0. the original and refined oil isas toliowsz' .OrIdnll s c vity .l 'o. mty sybolt 210 F.

Viscosity gravity constant- 0. Carbon residue 2.

Banned oil to 0.2m

I can and 75:25, the miscibility temperature characteristic oi the composite solvent being higher than that of ethylene dichloride alone, and finallyseparating the solvent, together with constituents extracted from the oil, from the extracted oil.-

ERIC 3. HJERPE. WILLIAM A. ,GRUSE. 

